Re: [boost] [c++11]

Subject: Re: [boost] [c++11]
From: Jonathan Wakely (jwakely.boost_at_[hidden])
Date: 2013-06-18 05:37:16

On 18 June 2013 08:33, Thomas Heller wrote:
> On Mon, Jun 17, 2013 at 11:54 PM, Niall Douglas <ndouglas_at_[hidden]>wrote:
>> Now, nothing in proposed Boost.AFIO uses variadic templates in a way not
>> replaceable with preprocessor programming. However it very /nearly/ did: I
>> had this neato bit of evil variadic instantiation which let you convert an
>> unknown set of trailing args into a std::tuple<> for storage, then /unpack/
>> said std::tuple<> back into an unknown set of trailing args, all with
>> perfect forwarding. Effectively it was a compile-time std::function<>
>> implementation.
>>
>
> That is *very* easily achievable with the preprocessor. The outstanding
> feature here, IMHO, is the perfect forwarding, which is of course not
> possible with C++03. In any case, I couldn't think of how you'd unpack the
> tuple to call the function without the preprocessor. Could you please show
> me a code snippet how this could be done?

Very, very easily, see the apply() example in [intseq.general] in the
C++14 draft, taken from
http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2013/n3658.html

Doing that with the preprocessor instead would be ... I don't have a
polite way to say it.